#include<bits/stdc++.h>
#define sd(n) scanf("%d",&n) 
#define sld(n) scanf("%lld",&n)
#define pd(n) printf("%d", (n))
#define pld(n) printf("%lld", n)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second
const int N=2e5;
#define INF 0x7fffffff
typedef long long int ll;
using namespace std;
//----------------------------------------------------------------------------//

void solve()
{
	int a,b,c,d;
	sd(a);sd(b);sd(c);sd(d);
	double ans1=0.0;
	if(a>=c&&b>=d)
	{
		ans1=max(1.0*(c*d)/(a*b),(1.0*(a-c)*(b-d)/(a*b)));
	}
}

int main()
{
	int T;
	sd(T);
	while (T--)
	{
		solve();
	}
	return 0;
}